JP5054500B2 - Pressure-controlled flow standard - Google Patents

Description

The present invention relates to a pressure controlled flow datum used for calibration of the various flow controller for semiconductor manufacturing equipment and chemicals manufacturing apparatus used in chemical manufacturing apparatus or the like.

  In semiconductor manufacturing apparatuses and the like, so-called calorific flow rate controllers (MFC) and pressure flow rate controllers (FCS) are often used as flow rate controllers for various process gases. In particular, the latter pressure type flow rate controller has a simple structure and has excellent characteristics such as responsiveness, measurement accuracy, service life, and maintainability, and is widely used.

By the way, these thermal flow controllers and pressure flow controllers are usually shipped to the market after performing flow rate calibration one by one using a flow standard.
On the other hand, as will be described later, the flow rate standard used for flow rate calibration is a. A method (build-up method or ROR method) for calculating the flow rate of the gas fed from the pressure of the gas accumulated in the chamber and feeding the gas into the chamber; A method of discharging the gas stored in the chamber and calculating the flow rate of the released gas from the change in the chamber weight (gas flow reduction method); Various standards have been developed using a method (gravimetric method) that sends gas into the chamber and calculates the flow rate of the gas sent from the change in the weight of the chamber. After calibrating the flow rate of the flow controller related to its manufacture using a flow rate reference device independently selected by the manufacturer, the product is shipped to the end user.

  For this reason, in production facilities that use flow controllers, if the manufacturer of the flow controller is determined at the time of installation, the same flow controller from the same manufacturer must be used for refurbishing or partially updating the equipment. The flow controller of another new manufacturer cannot be easily applied. For this reason, there arises a problem that the facility cost cannot be reduced. This is because the flow rate standard used for calibration varies from manufacturer to manufacturer, so even if the specifications are the same, actual flow values will vary slightly, and high-precision flow control like semiconductor manufacturing equipment. This is because it is difficult to mix and use flow controllers from different manufacturers.

There are various problems associated with the flow rate calibration of the flow rate controller due to the flow rate reference device itself.
That is, these flow rate reference devices are configured using the normal build-up method or the weight method as described above. For example, in the former build-up method, as shown in FIG. 8, first, a gas G having a set flow rate is supplied into a chamber C having a predetermined internal volume V (l) through a flow rate controller MFC that performs flow rate calibration. From the reading of the pressure gauge P, the relationship between the supply time T and the chamber internal pressure P is obtained.
Next, from the measurement results of the supply time T and the internal pressure P as shown in FIG. 9, the pressure increase rate ΔP / Δt of the chamber internal pressure is obtained, and the following equation (1) is obtained using the pressure increase rate ΔP / Δt. The flow rate Q (sccm) of the flow rate controller MFC is calculated from the flow rate, and the read value of the flow rate controller MFC is calibrated based on this calculated value.

However, many problems still remain in this build-up method, and among them, the first problem is that it is difficult to accurately measure the gas temperature T in the chamber C.
That is, when the gas temperature T is measured at the center in the chamber C and when the gas temperature T is measured in the vicinity of the wall surface of the chamber C, the measured value of the gas temperature T is considerably different. When the temperature T changes by 1 ° C., the flow rate Q (sccm) is about 0.33% S.V. P. It will change.

  The second problem is that the measurement accuracy of the pressure gauge (baratron) P is low, and the pressure increase rate ΔP / Δt varies with each measurement. That is, the pressure gauge (Baratron) P has a unique temperature characteristic and pressure rise characteristic (linearity). For this reason, when the pressure increase range (pressure increase span) and the pressure measurement conditions are different, the form of the curve showing the measurement results in FIG. It will be. Further, when the flow rate of the flow rate measuring device is increased, a large chamber C is required. Conversely, when the chamber C is reduced, problems such as a long time required for measurement occur.

  The third problem is that the flow rate value (calibration flow rate) actually calculated by the equation (1) is different for each measurement. That is, even if the experimental system, flow rate, measurement time, measurement pressure range, etc. are exactly the same, in reality, the calibration flow rate value will fluctuate only by changing the flow range of the pressure flow controller, and as a result There is a difficulty that high-precision flow rate calibration cannot be performed.

  FIG. 10 shows an example of the flow rate calibration test result of the flow rate controller by the build-up method. Even if the calibration flow rate is adjusted so that the flow rate error becomes zero at the flow rate setting of 100%, the flow rate setting value The results show that the error (% FS) increases as SET (%) changes.

  On the other hand, separately from the flow rate standard based on the build-up method, a gas weight reduction method is used in which the weight of the gas supply source (gas cylinder) is measured and the gas flow rate Q (sccm) is obtained from the weight reduction value. On the contrary, a flow rate reference device using a weight method in which gas is supplied into a chamber and a gas flow rate Q (sccm) is obtained from an increase value of the chamber weight has been developed.

  However, the flow rate reference device using the gas weight loss method or the weight method has a problem that a high-precision weighing device is required, the device is large, and a long time is required for measurement.

As described above, the flow rate reference device used for the flow rate calibration of the flow rate controller is different for each manufacturer of the flow rate controller, and the accuracy of the used flow rate reference device itself is relatively low. As a result, each time the flow controller model (manufacturer or model) to be used changes, the flow measurement value fluctuates. For example, in the field where the manufacturing process is miniaturized, such as the semiconductor manufacturing process, it such differences in flow calibration for slight flow controller of (error), so that a strong negative influence on the entire process.

  Further, in semiconductor manufacturing facilities and the like, a lot of corrosive gas is used as a process gas. For this reason, the flow controller is also subject to many errors due to corrosion, and there is a problem that the process is adversely affected. This also applies to the reference flow rate controller (master controller) used in the pressure-controlled flow rate reference device. When the flow rate calibration gas is a corrosive gas, the orifice hole of the master controller The morphology and inner diameter may change due to corrosion, or the orifice hole may be blocked by corrosion products, resulting in loss of function as a master controller.

Japanese Patent No. 3580645 JP-A-11-63265 JP 2000-137528 A

The present invention relates to the above-described problems in the reference flow meter based on the conventional build-up method, gas weight loss method, and weight method. The accuracy of the flow standard used is low, and the structure and type of the flow standard used by each flow controller manufacturer differ, so errors between the flow controllers can adversely affect the semiconductor manufacturing process. , B. A flow controller with a corrosive gas is to solve the problem that the control accuracy of the flow rate decreases quickly, and the pressure control has high flow control accuracy and excellent operational stability. The pressure control type flow rate reference device that made it possible to unify the flow rate calibration accuracy of the flow rate controller by configuring the pressure control type flow rate reference device with the flow rate type control device as the reference flow rate controller (master flow rate controller) Is intended to provide.

The invention of claim 1 includes a pressure controller for adjusting the pressure of a calibration gas from a calibration gas supply source , a tank having an internal capacity of at least 1 liter provided downstream of the pressure controller, and a downstream of the tank. A thermal mass flow meter provided on the side, a connection port provided on the downstream side of the thermal mass flow meter, to which the upstream side of one calibrated flow controller is connected, and downstream of the calibrated flow controller a tank having a connection port side is connected, a reference pressure type flow controller upstream side connected to the connecting port, the content of at least 1 liter provided on the downstream side of the reference pressure type flow controller, the A vacuum evacuation device provided on the downstream side of the tank is a basic configuration of the invention.

  According to a second aspect of the present invention, in the first aspect of the invention, the reference pressure type flow rate controller is configured by connecting a plurality of reference pressure type flow rate controllers in parallel.

  According to a third aspect of the present invention, in the first aspect of the invention, the fluid inlet side and the outlet side of the reference pressure type flow rate controller are directly connected by a bypass circuit.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the reference pressure type flow rate controller includes an orifice, a control valve provided upstream of the orifice, a pressure detector provided between the control valve and the orifice, from detected pressure P ₁ of the detector flow Q as well as calculation as Q = KP 1 _(where K is a constant), the difference between the flow rate signal Q obtained by the arithmetic and flow command signal Q _S as a control signal Qy in the control valve is composed of a calculation control unit for outputting to the drive unit, the orifice upstream by opening and closing the upstream pressure P ₁ and the ratio of the downstream pressure P ₂ being maintained at below the critical pressure ratio of the controlled fluid said control valve orifice adjust the side pressure P _1, it is obtained by a reference pressure type flow controller arrangement for controlling the fluid flow rate Q of the orifice downstream side.

  The invention of claim 5 is the invention of claim 1, wherein the vacuuming device is a vacuum pump or a vacuum chamber.

  In the present invention, one or more reference pressure flow controllers are connected in parallel and used as a master reference flow controller. As a result, the flow rate control accuracy is ± 0.25% S.D., fully utilizing the excellent flow rate control accuracy of the pressure type flow rate control device. P. The following flow rate reference device for flow rate calibration can be manufactured at a very low cost.

  In addition, since the reference pressure flow controller with high flow control accuracy is used as the master reference flow controller, extremely stable flow control accuracy can be obtained even if the temperature or pressure of the fluid fluctuates. Compared with the flow rate standard based on the up method, the gas weight loss method, or the weight method, the flow rate controller can be calibrated with high accuracy and stability.

  Furthermore, the corrosion resistance is improved by forming a gold plating film with a thickness of 2-5 μm on the inner wall surface where the fluid inside the reference pressure flow controller that forms the master reference flow controller is in contact with. The flow rate calibration can also be performed safely and with high accuracy. For example, when used for flow rate calibration of a flow rate controller for semiconductor manufacturing equipment, it is possible to significantly improve the quality of semiconductor products and reduce manufacturing costs. .

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 is an overall configuration diagram of a pressure control type flow rate reference device according to the present invention. In FIG. 1, 1 is a calibration gas supply port, 2 is a pressure controller, 3 is a tank , 4 is N ₂ gas supply 5 is a thermal mass flow meter, 6 is a purge gas supply port, 7 is a purge gas discharge port, 8 is a flow rate controller to be calibrated, 9 is a reference pressure type flow rate controller (master pressure type flow rate controller), and 10 is a tank , 11 is a connection port of a vacuuming device, 12 is a bypass circuit, 13 is a connection port of a flow rate controller to be calibrated, AV _{1 to} AV ₂₆ are on-off valves, F ₁ and F ₂ are filters, and PT is a pressure detector. .

The tanks 3 and 10 are provided to prevent a shortage of the primary supply pressure of the flow rate controller 8 to be calibrated and an increase in the secondary pressure of the reference pressure type flow rate controller (master pressure type flow rate controller) 9. In this embodiment, a tank having a capacity of 1 to 3 l is used.

  The thermal mass flow meter 5 is a preliminary flow rate controller for confirming whether or not there is a serious trouble in the reference pressure type flow rate controller (master pressure type flow rate controller) 9, and in this embodiment, Two thermal mass flowmeters of 10 SLM and 200 SCCM are used in parallel.

  The reference pressure type flow rate controller (master pressure type flow rate controller) 9 is a combination of a plurality of pressure type flow rate controllers in parallel, and the flow rate up to 10 SLM is changed to 12 reference pressure type flow rate controllers 9. Therefore, it is configured to cover.

When calibrating the flow rate of the flow rate controller 8 to be calibrated, first, a vacuuming device such as a vacuum pump or a vacuum chamber (not shown) is connected to the vacuuming device connection port 11, and 2 of the reference pressure type flow rate controller 9. While evacuating the next side, the flow rate of the reference pressure type flow rate controller 9 is selected so that the flow rate is close to the rated flow rate of the flow rate controller 8 to be calibrated, and the on-off valves AV _{11 to} AV ₂₂ are appropriately opened. .

Next, for calibration with a flow rate substantially close to the rated flow rate of the flow rate controller 8 to be calibrated from the calibration gas supply source through the calibration gas supply port 1 , the pressure controller 2, the volume 3, and the thermal mass flow meter 5. the gas is circulated to be calibrated flow controller 8, by comparing the reading and reading and Hiko forward flow quantity controller 8 of the reference pressure type flow controller 9, the flow rate calibration of the calibration flow controller 8.

100% F. above. When the flow rate calibration in S is completed, the supply flow rate from the calibration gas supply port 1 is adjusted, and at the predetermined set flow rate (% FS), both controllers 8 and 9 are respectively the same as described above. perform flow contrast, the flow rate calibration of the school forward flow quantity controller 8.
During the flow rate calibration, the secondary pressure P ₂ of the reference pressure type flow rate controller 9 is maintained at ½ or less of the upstream side pressure P ₁ , and the orifice ( The calibration gas flowing through (not shown) is in a critical state.

FIGS. 11 and 12 show the overall configuration of the reference pressure type flow rate controller 9, which is known as a pressure type flow rate controller such as Japanese Patent No. 3580645 and Japanese Patent Laid-Open No. 11-63265. That is, the flow rate _Q C = _KP 1 on the primary side pressure _{P 1} and the arithmetic control device H from the primary side gas temperature _{T 1} of the orifice OL (K is a constant determined by the orifice O L) is calculated and a set flow rate Qs The opening of the flow control valve CV is adjusted so that the difference Qy = Qs−Qc becomes zero. In addition, as a pressure type flow controller, as shown in FIG. 12, each member CV, H, P, T, OL, etc. are assembled | attached integrally.
Further, the pressure type flow rate controller is provided with a mechanism for automatically detecting the output value of the flow rate output signal and clogging of the orifice OL, and so-called self-diagnosis of the flow rate (Japanese Patent Laid-Open No. 2000-137528). ).
As described above, since the pressure type flow rate controller itself is known, its detailed description is omitted here.
Further, the pressure type flow controller has a relatively small measurement error with respect to temperature and pressure fluctuations compared to other types of flow controllers such as thermal flow controllers, and the Since it is small in size and can handle various gases with the same controller, it is optimal for use as a flow control reference device.

Thus, in the reference pressure type flow rate controller 9 used in the present invention, a gold plating film having a thickness of 2 to 5 μm is formed on the entire surface of the gas contact portion.
The gold plating film may be formed by any method. In the present invention, a gold plating film having a thickness of 1 to 3 μm is formed by a so-called chemical plating method.

  By the way, it is a well-known matter that a gold plating film etc. hold | maintain corrosion resistance. Therefore, the inventors of the present application apply this known matter to a pressure type flow rate controller having an orifice as an essential component, and enhances the corrosion resistance against all corrosive gases by applying gold plating to the gas contact part. It was conceived that the flow rate control accuracy can always be maintained at a high level even when corrosive gas is circulated by preventing changes in the orifice hole clogging, diameter size, form, and the like.

  The reference pressure type flow rate controller (master pressure type flow rate controller) 9 used in the present invention was developed based on the above idea, and forms a gold plating film with a thickness of 2 to 5 μm on all the gas contact parts. It is characterized by that.

Table 1 shows an example of main test items performed on the reference pressure type flow rate controller (master pressure type flow rate controller) 9 according to the present invention and its judgment criteria.
In addition, four reference pressure type flow rate controllers 9 were manufactured as test samples.

  Tables 2 to 5 show the results of the test.

Next, the corrosion resistance test method of the reference pressure type flow rate controller 9 according to the present invention and the test results will be described.
Referring to FIG. 3, first, the reference pressure type flow rate controller 9 that has completed each test (accuracy confirmation test) 17 in Tables 2 to 4 is left in a clean room for 18 hours, and then cycled by N ₂ gas. After purging 19 and further filling 20 with actual gas for 24 hours, cycle purge 19 with N ₂ gas is performed again, and accuracy check test 17 is performed again. The gas flowing out from the secondary side is received by the wafer, and metal contamination existing on the wafer is inspected 21 by the metal contamination detection device.

Each of the cycle purges 19 is continuously purged with N ₂ gas at a pressure of 0.1 MPa for 1 minute, then filled with 0.1 MPa of N ₂ gas, and then kept in a vacuum state for 10 seconds 10 times continuously. And finally purging with 0.1 MPa of N ₂ gas for 1 minute.

The corrosion test cycle shown in FIG. 3 is continuously performed by changing the actual gas to be supplied in the order of HCL, CL ₂ , HBr, and HF (4 cycles using four kinds of actual gases), and The processing operation with the same content was repeated three times.

  FIG. 4 shows a change state of the flow rate control accuracy after the corrosion test in which HBr is sealed for 24 hours in the reference pressure type flow rate controller 9 which is not subjected to the gold plating process. It can be seen that an error of about 20 (% S.P.) or more is caused by the clogging of the corrosion product into the orifice due to the time sealing.

  FIG. 5 shows a change state of the flow rate control accuracy before and after enclosing the HBr gas for 24 hours when a gold plating film having a thickness of 2 μm is formed. As is clear from the comparison with FIG. In the case of forming a gold plating film with a thickness of 2 to 5 μm, it can be seen that the influence of corrosion by HBr gas on the flow rate control accuracy can be almost ignored at a flow rate of 20 (% SP) or more.

In the case of gold plating, a film thickness of about 2 to 5 [mu] m is sufficient, and even if the thickness is 5 [mu] m or more, the corrosion resistance does not increase so much, and the economy is deteriorated.
Therefore, the thickness of the gold plating film is preferably selected to be 2 to 5 μm.
Similarly, the gold plating film may be formed by any method, but a chemical plating method using a plating solution is advantageous in terms of work process and can be widely applied to a pressure type flow rate controller.

  For reference, the same corrosion resistance test was performed on a reference pressure type flow rate controller in which a nickel plating film (thickness: 2 μm) was formed on the gas contact portion instead of gold plating. FIG. 6 shows the result, and it was found that the flow rate error (% SP) decreased by about −5% in the nickel plating film and could not be put into practical use.

Next, the relationship between the flow rate accuracy and the number of corrections in the low flow rate region of the reference pressure type flow rate controller 9 was investigated.
In the pressure type flow rate control device, if the gas flow through the orifice is under a critical condition and the shape of the orifice (diameter or shape on the gas inlet side) is not changed, the flow rate through the orifice is the pressure P ₁ on the primary side of the orifice. Therefore, a relatively stable flow control accuracy can be basically obtained.
However, from the viewpoint of the use as the reference pressure flow rate controller 9, higher control accuracy, for example, a set flow rate of 1%% S.P. P. ± 0.25% S.E. even in the low constant flow region. P. Since the following control accuracy is desired, it was examined whether or not the realization was possible by repeating the correction.

  Table 6 shows the number of corrections for the reference pressure type flow rate controller 9 and the set flow rate 1% S.E. P. FIG. 7 shows the test result with the flow rate accuracy at the time of FIG.

  In Table 6 and FIG. 7, σ is the standard deviation, and the error is% F. S. Value. As is apparent from FIG. 7, by repeating the correction, ± 1 dgit = ± 0.065% F.V. S. It was found that it was possible to suppress the error to within. As a result, the reference pressure type flow rate controller 9 used for the test was ± 0.25% S.P. P. It was confirmed that the flow rate control accuracy can be sufficiently provided.

Pressure control wherein the flow rate datum according to the present invention are those applicable to calibration reference device of any type of flow controller, also the reference pressure type flow controller for use in the present invention, a corrosive gas It can be widely applied as a flow rate controller for the equipment used.

1 is an overall configuration diagram of a pressure-controlled flow rate reference device according to the present invention. It is a diagram which shows the result of the flow precision test (% FS) of the reference pressure type flow controller used for this invention. It is explanatory drawing of the corrosion resistance test of the reference | standard pressure type flow controller used for this invention. It is a diagram which shows the change state of the flow control error after enclosing for 24 hours of HBr gas when there is no gold plating film. It is a diagram which shows the change state of the flow control accuracy after enclosing HBr gas for 24 hours at the time of forming a gold plating film. It is a diagram which shows the change state of the flow control accuracy after enclosing HBr gas for 24 hours at the time of forming a nickel plating film. It is a diagram which shows the relationship between the frequency | count of correction | amendment of a reference | standard pressure type flow controller, and flow control accuracy. It is explanatory drawing of the flow volume calibration method based on the buildup method. It is a diagram which shows an example of the chamber pressure increase rate in the buildup method. It is a diagram which shows an example of the flow measurement accuracy based on the buildup method. The basic composition of a pressure type flow controller is shown. It is a longitudinal cross-sectional schematic diagram of a pressure type flow controller.

Explanation of sign

1 Calibration gas supply port 2 Pressure controller 3 Tank 4 Filter 5 Thermal mass flow meter 6 Purge gas supply port 7 Purge gas discharge port 8 Calibrated flow rate controller 9 Reference pressure type flow rate controller (master pressure type flow rate controller)
10 tank 11 connection port 12 of vacuum evacuation device bypass circuit 13 connection port AV ₁ -AV _{26 on-} calibration flow rate controller on-off valve F ₁ , F ₂ filter PT pressure detector

Claims (5)

A pressure controller for adjusting the pressure of the calibration gas from the calibration gas supply source , a tank having an internal capacity of at least 1 liter provided downstream of the pressure controller, and a thermal mass provided downstream of the tank A flow meter, a connection port provided on the downstream side of the thermal mass flow meter and connected to the upstream side of one calibrated flow rate controller, and a connection port connected to the downstream side of the calibrated flow rate controller A reference pressure type flow controller whose upstream side is connected to the connection port, a tank having an internal capacity of at least 1 liter provided downstream of the reference pressure type flow controller, and provided downstream of the tank Pressure-controlled flow rate reference device composed of a vacuuming device   The pressure control type flow rate controller according to claim 1, wherein the reference pressure type flow rate controller is configured by connecting a plurality of reference pressure type flow rate controllers in parallel.   The pressure control type flow rate reference device according to claim 1, wherein the fluid inlet side and the outlet side of the reference pressure type flow rate controller are directly connected by a bypass circuit.   A reference pressure type flow rate controller includes an orifice, a control valve provided upstream of the orifice, a pressure detector provided between the control valve and the orifice, and a detected pressure P of the pressure detector. ₁ To flow rate Q from Q = KP ₁ (Where K is a constant) and the flow rate command signal Q _S And an arithmetic control device for outputting the difference between the calculated flow rate signal Q as the control signal Qy to the drive portion of the control valve, and the upstream pressure P of the orifice ₁ And downstream pressure P ₂ The orifice upstream pressure P by opening and closing the control valve while maintaining the ratio to the critical pressure ratio of the controlled fluid. ₁ The pressure control type flow rate reference device according to claim 1, wherein the reference pressure type flow rate control device is configured to control the fluid flow rate Q downstream of the orifice.   2. The pressure-controlled flow rate reference device according to claim 1, wherein the evacuation device is a vacuum pump or a vacuum chamber.

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